It's unlikely that it has anything to do with the "calibre6" style, but since you haven't posted the css for this style it's hard to tell you for certain what's going on. It's more likely that ADE doesn't acknowledge a <br> inside an empty <div>. (and the Sony uses the same rendering engine as ADE)

You can use search replace to replace this string:

Code:

<div[^>]*>\s*<br(\s?/)?>\s*</div>

With this:

Code:

<p></p>

But then you also need to enable the 'format scene breaks' option under heuristics. I can add this case to the format scene breaks option so it works in the future.

I never put anything in the "extra css" field, just use the defaults Calibre has. I usually manage to muddle through with the little bit of info I understand from reading this board, but confess I don't do anything too fancy. And everytime I think I am beginning to undertand regular expressions, it just makes me realize how much more I have to learn.

I never put anything in the "extra css" field, just use the defaults Calibre has. I usually manage to muddle through with the little bit of info I understand from reading this board, but confess I don't do anything too fancy. And everytime I think I am beginning to undertand regular expressions, it just makes me realize how much more I have to learn.

Use Sigil, it makes the edit process simple.
Or
select the book in the Library (view) of Calibre: Tap 'T' (tweak)
Explode the book. Locate stylesheet1.css
BTW there appears to be a missing space (required) before the closing /> in the BR

The code makes even less sense now.
BTW Conversion can only work so many wonders

GIGO

You have some 'G' in your original.

IMHO Top, Bottom Margins or Padding the preceding or next block is the way to space out paragraphs,headers ...

calibre6 is a Block with a Line height increase which would be OK for the Div, but NOT for the BR which is part of the (non-existent) content within the div. If yo must stay with the Div, simply replace the BR with a <p>&nbsp;</p> ( a space has height)

If yo must stay with the Div, simply replace the BR with a <p>&nbsp;</p> ( a space has height)

That's essentially why I suggested the search and replace with the format scene breaks option - it would do this for you during conversion, but you wouldn't want to stick &nbsp; in the replace box, entities can sometimes have un-desirable effects in the middle of conversion.